1. Field of the Invention
The invention relates generally to efficient means for the generation of electrical or other power by utilizing energy from subterranean geothermal sources and, more particularly, relates to arrangements in which enthalpy losses caused by pressure losses and sub-cooling in the condenser system are restored by passing the expanding down-well turbine exhaust through the condensate liquid feeding the primary or surface heat exchanger.
2. Description of the Prior Art
Generally related prior art geothermal power generation systems have been discussed in recent U.S. patents assigned to Sperry Corporation including:
H. B. Matthews--U.S. Pat. No. 3,824,793 for "Geothermal Energy System and Method," issued July 23, 1974; PA1 H. B. Matthews--U.S. Pat. No. 3,989,020 for "Geothermal Energy System and Method" issued Aug. 5, 1975; PA1 R. Govindarajan, J. L. Lobach, K. E. Nichols--U.S. Pat. No. 3,905,196 for "Geothermal Energy Pump Thrust Balance Apparatus," issued Sept. 16, 1975; PA1 J. L. Lobach--U.S. Pat. No. 3,908,380 for "Geothermal Energy Turbine and Well System," issued Sept. 30, 1975; PA1 H. B. Matthews--U.S. Pat. No. 3,910,050 for "Geothermal Energy System and Control Apparatus," issued Oct. 7, 1975; PA1 H. B. Matthews--U.S. Pat. No. 3,939,334 for "Geothermal Energy Control System and Method," issued Feb. 17, 1976; PA1 H. B. Matthews--U.S. Pat. No. 3,939,659 for "Geothermal Energy System Fluid Filter and Control Apparatus," issued Feb. 24, 1976; and PA1 K. E. Nichols--U.S. Pat. No. 3,961,866 for "Geothermal Energy System Heat Exchanger and Control Apparatus," issued June 8, 1976.
Systems of the listed patents may be improved by use of the present invention and will be further discussed in the present specification. In general, they comprise geothermal energy recovery systems making use of thermal energy stored by subterranean heat sources in hot, solute-bearing well water to generate super-heated vapor from a surface-injected flow of a clean liquid; the super-heated vapor is then used to operate a turbine-driven pump within the well for pumping the hot brine at high pressure and always in liquid state to the earth's surface, where it transfers its heat in a binary closed-loop, heat-exchanger turbine-alternator combination for generation of electrical power. Residual brine is pumped back into the earth, while the clean, cooled liquid is regenerated at the surface-located system and is returned to the deep well pumping system for generating vapor and also may be used for lubrication of fluid bearings supporting the turbine-driven pump system.
More recently, H. B. Matthews introduced an additional type of geothermal energy extraction concept in his U.S. Pat. No. 4,142,108, issued Feb. 20, 1979 for a "Geothermal Energy Conversion System" in which the present invention may also be advantageously employed. In the latter Sperry Corporation patent, Matthews describes a gravity head geothermal energy recovery system of improved efficiency again making use of thermal energy stored in hot, solute-bearing well water as it is pumped upward to the earth's surface, now through an extended heat exchange element for continuously heating a downward flowing organic working fluid to a supercritical state. Some of the energy of the latter fluid is used within the well for operating a turbine-driven pump for pumping the hot, solute-bearing well water at high pressure and in liquid state to the earth's surface, where it is finally reinjected into the earth in another well. The temperature difference between the upward flowing brine and the downward flowing organic working fluid is maintained finite in a predetermined manner along the subterranean extended heat exchange element. After driving the deep-well turbine-driven pump, the organic fluid arises to the earth's surface in a thermally insulated conduit; at the earth's surface, vapor turbine electrical power generation equipment is driven by the ascending organic fluid, after which it is returned into the well for reheating in the extended heat exchanger. The use of an organic working fluid in the gravity head well system achieves efficient low-temperature operation in wells wherein the brine reaches only moderate temperature and this operation is further improved according to the present invention.